DESCRIPTION: The goals of specific aim 1 (project A) are to carefully state the intermediates in nuclear pore assembly (using chemical staging reagents such as wheat germ agglutinin, BAPTA, and low temperature) and to identify soluble factors that promote pore formation and stabilization. The goal of specific aim 2 (project B) is to test the roles of the membrane-embedded nucleoporins, gp120 and pom 121, in the membrane fusion' event that is thought to generate the pore. The goal of specific aim 3 (project C) is to identify and analyze soluble nucleoporins that associate in a functionally significant manner with gp120 and pom 121.